Compound blower.



Patented tm19, 1915.

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C. V. KERR. COMPOUND BLOWER.

APPLICATION FILED 00T. 7. 1913.

Patented Jan. 19, 1915.

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CHARLES -VOIJNEY KEER, OF WELLSVILLE, NEW YORK.

' 'COMPO'UND .BLOWER Specication of Letters Patent.

,Patented J all, 19, 1915.

f'Application led'ctober 7, 1913. =Serial No. 793-1843.

To all whom it may concern Be it known that I, CHARLES 'VoLNnY KERR, a citizen of the United States, residing at .Wellsville, New York, have invented a certain new and useful Compound Blower, of which the following is-a specification.

The principal object of the inventionl is to provide a blower capable of' producing with great eiiciency .a--relativelyhigh pressure. The invention provides a compact and efficient' blower adaptedto be used withsteam turbines or vhigh speed motor drive, and to produce the relatively high pressures required by gas works, foundries, forge shops and similar utilities. -For lower pressures, suoli as those required by boiler furnaces, a simpler, single stage -propel-ler type of blower is usually sufficient. But,'for higher pressures for the purposes mentioned, -a -multi-stage or compound constructlon 1s deute. .For lower speeds the capacity variesdirectly with lthe speed .and :the lpressure with the square ofthe speed.

In ybuilding -up final pressure, the discharge velocities from the propellers and from the centrifugal blades-are divided according to 1the rule that the '.sum of the squares of the two discharge velocities lmust v equal the square of the velocity' corresponding to the final pressure des-ired. 4-In connection with suitable centrifugal blades,?I nd it advantageous-to employ as initial com- -pressors,fimpellers having blades of concave face, increasing pitch form, described hereinafter.

I will-now describe one structure which constitutes an exemplifying embodiment of ymy invention, and itis to be understood that many modifications maybe Ira-de without departing from the invention.

Figure 1 isaside elevation of. a compound blower embodying the invention. Fig. 2 is verticaljsection. Fig. 3 is an enlarged side elevation of the rotor. Fig. Llis a vertical sectlon of the same on the same scale. Fig. 5 1s a top end view of one ofthe propeller blades. Fig. 6 is a section of such ya blade atthe-base, and Fig. 7 isa section yofsueh a blade-at the top. f

Reference .character 1 designates a 4discharge' casing of volute form, Ihaving dis- -charge outlet 2. This casing is -aperture'd atY each side, and in each aperture is fitted aplate 3, carrying 'a bell-mouthed inlet or supply ,opening 4. These bell-mouthed inlets contribute to high efficiency by reduc- .'ing eddy-lossesvin the'entering air. lThese plates also vsupport fon suitably larranged arms 5, bearing boxes "6 containing the shaft-bearings 7. These bearings are copiously 'oiledby ring oilers, orot-herfsuitable means, and to preventescape' of oil toward the 'fansthe bea-ringsl -are preferably provided -with stufiing boxes adjacent to the -propellers, one form "of such oil sealing means 4being fully described in my prior -l-application, Serial No. 785,008, filed August In bearings 7 the rotor shaft 10 is mounted, and upon this sha-ft is keyed a sleeve 11 having at-each end a hub 12. These hubs are vprovided vwith a plurality of peripheral axial'slots 13, in which are secured the bases of= blades 14 of thepropellers or initial compressors.

The blades are secured inthe hub slots in yany suitable Way. The shape of the blades is of'great-importance. As show-n in Figs. r5, 6 and 7, at the-periphery where the linear speed of the blade is'relatively great, it has la relatively-small pitch angle,while atzthe base wherel the speed is relatively less it has a suitably greater pitch. Preferably, the

'impelling face of the' blade is curved or ooncave, or, otherwise eXpressed,-the discharg- -ing edge of' the blade is'bent forward, 'giv-v ing in 4effect an increase ofthe face pitch of the-blade from the cutting edge tothe discharge edge. In this Way, theair is accelerf l ated as its passes across the face of the blade,

and at the same time thescrew 4'form or twist of theblade-serves to give thesame propelling impulse to discharged lair at alll radial points. Otherwise described, the blades-have concave faces,the curvature of which increases from tip'to base, .and the vaverage pitch .angle of the blades also-increases from tip to base. The initial compressors, therefore, havingimpeller blades of the described form, very eiliciently deliverair inward at suitable pressure to be in turn further acted on and compressed by the secondary or centrifugal blades, as will be described. `Without impellers having blades of suitable form, centrifugal blades parallel to the shaft as usually employed, and run at high speed, would move too fast to pick up air and deliver it with high elhciency. But by employing the above-described impeller blades to force air into the suction of the centrifugal blades, the centrifugal blades may be provided in suitably large number and with a relatively short radial length and given the backward directed surface which has'been found most efficient in centrifugal compressor work. rlhe capacity of the impeller blades may be and should be made such that the suction of the centrifugal blades is always crowded.

Hubs 12 with blades 14C constitute a propeller or initial compressor 13 at each side of the casing, and these are, of course, arranged so that they both draw air inward through suction inlets l1. -At the periphery of propeller blades 14 are angular side pieces 16. The cylindrical portions of these side pieces are welded, riveted or otherwise suitably iiXed to the tips of the propeller blades, the flat ring-shaped portions 17 of the side pieces providing betweenlthem an annular rotating nozzle discharging into the cas-v ing, and between such disks and in such annular nozzles are placed blades 18 constituting the centrifugal wheel or secondary compressor, rlhe ends of these blades may be bent at an angle as shown at 19 (Fig. 4), and riveted., welded or otherwise suitably secured to disks 17.r rllhe form and arrangement of the centrifugal blades are sufficiently shown in the drawings. llt should be mentioned particularly, however, that to reduce noise the number of blades in the propellers and in the centrifugal wheel is perfectly different. For instance, in the particular example shown there are twentyfour blades in the centrifugal wheel and sixteen blades in each of the propellers.

The centrifugal blades 18 receive air discharged by the propeller wheels toward the center of the rotor and in a path spirally outward in the direction of rotation, this initially compressed air being at a pressure of several inches water gage. rl`he centrifugal wheel in turn discharges this air at a pressure of, say, about twenty-five inches water gage into the casing, and the volute casing directs this air without loss by eddy currents to the discharge opening 2. Easy endwise removal and replacement of the rotor is permitted by removal of either of the side plates 3. The composite two-stage Wheel, it will be noticed, is assembled as a unit upon sleeve 11. The ends of the cymaarre lindrical parts of side pieces 16 revolve in annular countersinks 20 at the inner ends of suction openings 4.

lf claim:

1. ln a compound blower, the combina* tion of a volute casing having bell-mouthed inlet openings, a shaft, impeller thereon, one in each inlet opening, each impeller consisting of radial blades having concave working facesof helical pitch, said pitch increasing at all points of the blade from the inlet to the discharge edges to obtain an increased discharge head, and a centrifugal blower mounted to revolve with the impel lers and to receive air initially compressed by thev impellers and discharge it with increased pressure into the casing. 2. ln a compound blower, the combination of a volute casing, in one piece removable side plates therein, each provided with a bell-mouthed inlet opening, bearings carried by said plates, a shaft mounted in the bearings, impeller hubs on the shaft, impeller blades carried by said hubs, one set of blades revolving within each inlet opening, side pieces secured to the ends of said blades, and centrifugal blades arranged in an annulus between said side pieces, the outside diameter of the rotor thus formed being less than the diameter of the opening in the casing to receive one of the removable side plates whereby the rotor may be removed from the casing in an aXial direction.

3. ln a compound blower, the combination of a volute casing having opposite bellmouthed inletopenings, a shaft, a sleeve thereon provided with two impeller hubs,-

and also increasing at all points of theblade from the inlet to the discharge edge to obtain an accelerated discharge, side pieces of angular section secured to the tips of said blades and centrifugal blower blades parallel to the shaft and annularly arranged between said side pieces, said centrifugal blades discharginginto the casing.

4. lin a compound blower, the combination of a volute discharge casing having side openings, a plate removably secured in each opening, each plate having an inlet opening, shaft bearings one at each side of the casing, supports for said bearings carried by said plates, a shaft in the bearings, impeller hubs carried by the shaft, impeller blades on the hubs, angle pieces secured to the tips of the blades and centrifugal blower blades secured between said angle pieces parallel to the shaft axis the outer diameter of the rotor described being smaller than the openings in the casing to permit removal of the rotor in an axial direction.

5. A rotor for blowers and the like, comprising a rotatable shaft, impellers mounted thereon, each impeller consisting of a hub and impellerblades secured thereto and extending radially, rings having cylindrical and radial anges, said cylindrical anges being secured to the outer ends of said impeller blades, and centrifugal blades arl ranged parallel to said shaftand secured centrifugal blades, said impeller blades serving also to transmit ldriving power from said shaft through said rings to said centriugal blades.

6. A rotor for blowers and the like, com- Erising a revoluble shaft,` a sleeve thereon aving a flange at each end, impeller blades secured to said flanges, the blades having a` helical pitch and impelling surfaces of increased curvature from the entering to the leaving edges thereof, rings having cylinthe impeller blades and 'also radial flanges, a plurality of centrifugal blades parallel to radial flanges, the parts being so constructed and arranged that the impeller blades discharge toward each other into the suction of the centrifugal blades and also transmit driving power for the centrifugal blades through the rings.

CHARLES VOLNEY KERR.

Witnesses: v

H. R. FLINT, VoLNEY A. KERR.

drical flanges, attached to the outer ends of the shaft and secured to and between. said 

